High capacitance trench capacitor

ABSTRACT

A dual node dielectric trench capacitor includes a stack of layers formed in a trench. The stack of layers include, from bottom to top, a first conductive layer, a first node dielectric layer, a second conductive layer, a second node dielectric layer, and a third conductive layer. The dual node dielectric trench capacitor includes two back-to-back capacitors, which include a first capacitor and a second capacitor. The first capacitor includes the first conductive layer, the first node dielectric layer, the second conductive layer, and the second capacitor includes the second conductive layer, the second node dielectric layer, and the third conductive layer. The dual node dielectric trench capacitor can provide about twice the capacitance of a trench capacitor employing a single node dielectric layer having a comparable composition and thickness as the first and second node dielectric layers.

BACKGROUND

The present disclosure relates to a semiconductor structure, andparticularly to a trench capacitor structure including dual nodedielectric layers and methods of manufacturing the same.

Deep trench capacitors are used in a variety of semiconductor chips forhigh areal capacitance and low device leakage. Typically, a deep trenchcapacitor provides a capacitance in the range from 4 fF (femto-Farad) to120 fF. A deep trench capacitor can be employed as a charge storage unitin a dynamic random access memory (DRAM), which can be provided as astand-alone semiconductor chip, or can be embedded in a system-on-chip(SoC) semiconductor chip. A deep trench capacitor can also be employedin a variety of circuit applications such as a charge pump or acapacitive analog component in a radio-frequency (RF) circuit.

Deep trench capacitors are formed in a semiconductor substrate, whichcan be a semiconductor-on-insulator (SOI) substrate or a bulk substrate.Other semiconductor devices such as field effect transistors can beformed on the same semiconductor substrate, thereby enabling embeddingof deep trench capacitors into a semiconductor chip. Such embedded deeptrench capacitors enable various functionality including embeddeddynamic access memory (eDRAM) and other embedded electronic componentsrequiring a capacitor.

While deep trench capacitors provide a high capacitance per unit area,scaling of deep trench capacitors is difficult because maintaining thedepth of a deep trench becomes more difficult as the lateral dimensionof the deep trench are reduced. Thus, the capacitance per unit area of adeep trench capacitor employing a conventional structure has a limit.However, a capacitor structure having a greater capacitance per unitarea than currently available would free up more area for othersemiconductor devices, and thereby increase the device density inintegrated semiconductor circuits.

BRIEF SUMMARY

A dual node dielectric trench capacitor includes a stack of layersformed in a trench. The stack of layers includes, from bottom to top, afirst conductive layer, a first node dielectric layer, a secondconductive layer, a second node dielectric layer, and a third conductivelayer. The dual node dielectric trench capacitor includes twoback-to-back capacitors, which include a first capacitor and a secondcapacitor. The first capacitor includes the first conductive layer, thefirst node dielectric layer, the second conductive layer, and the secondcapacitor includes the second conductive layer, the second nodedielectric layer, and the third conductive layer. The first conductivelayer and the third conductive layer can be electrically connected, inwhich case the dual node dielectric trench capacitor is a two-nodecapacitor structure. The dual node dielectric trench capacitor canprovide about twice the capacitance of a trench capacitor employing asingle node dielectric layer having a comparable composition andthickness as the first and second node dielectric layers.

According to an aspect of the present disclosure, a structure includinga capacitor structure is provided. The capacitor structure includes: atrench located in a substrate; a first conductive layer contiguouslycontacting a bottom surface and sidewalls of the trench; a first nodedielectric layer contiguously contacting sidewalls of the firstconductive layer; a second conductive layer contiguously contactingsidewalls of the first node dielectric layer; a second node dielectriclayer contiguously contacting sidewalls of the second conductive layer;and a third conductive layer contiguously contacting sidewalls of thesecond node dielectric layer.

According to another aspect of the present disclosure, a method offorming a structure including a capacitor structure is provided. Themethod includes: forming a trench in a substrate; forming a firstconductive layer contiguously contacting a bottom surface and sidewallsof the trench; forming a first node dielectric layer contiguouslycontacting sidewalls of the first conductive layer; forming a secondconductive layer contiguously contacting sidewalls of the first nodedielectric layer; forming a second node dielectric layer contiguouslycontacting sidewalls of the second conductive layer; and forming a thirdconductive layer contiguously contacting sidewalls of the second nodedielectric layer, wherein the first conductive layer, the first nodedielectric layer, the second conductive layer, the second nodedielectric layer, and the third conductive layer collectively form acapacitor structure.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIGS. 1-11 are sequential vertical cross-sectional views of a firstexemplary structure according to a first embodiment of the presentdisclosure.

FIGS. 12-17 are sequential vertical cross-sectional views of a secondexemplary structure according to a second embodiment of the presentdisclosure.

FIGS. 18-24 are sequential vertical cross-sectional views of a thirdexemplary structure according to a third embodiment of the presentdisclosure.

DETAILED DESCRIPTION

As stated above, the present disclosure relates to a trench capacitorstructure including dual node dielectric layers and methods ofmanufacturing the same, which is now described in detail withaccompanying figures. It is noted that like reference numerals refer tolike elements across different embodiments. The drawings are notnecessarily drawn to scale.

As used herein, a “deep trench” is a trench that extends from a topsurface of a semiconductor-on-insulator substrate to a depth below abottom surface of a buried insulator layer as applied to asemiconductor-on-insulator substrate, or a trench that extends from atop surface of a bulk substrate and having a depth greater than 1micron.

As used herein, a first element is “electrically connected” or“electrically shorted” to a second element if the voltage at said firstelement is the same as the voltage at said second element under alloperating conditions of said first element and said second element.

As used herein, a first element is “electrically isolated” from a secondelement if the voltage at said first element is not affected by thevoltage at said second element under all operating conditions of saidfirst element and said second element.

As used herein, a “conductive” element has an electrical conductivitythat is greater than 10³ siemens per centimeter.

As used herein, a “refractive metal” refers to Ti, V, Cr, Zr, Nb, Mo,Ru, Rh, Hf, Ta, W, Re, Os, Ir, and alloys thereof.

Referring to FIG. 1, a first exemplary structure according to a firstembodiment of the present disclosure includes a substrate 8, a masklayer 6, and at least one deep trench 9. The substrate 8 includes atleast a substrate material layer 10 that includes a material having anelectrical conductivity less than 10³ siemens per centimeter (which isthe same as 10³/Ohm·cm).

In one embodiment, the substrate material layer 10 is a semiconductormaterial layer having an electrical conductivity from 10⁻⁸ siemens percentimeter to 10³ siemens per centimeter. For example, if thesemiconductor material layer is a silicon layer, the semiconductormaterial layer can be an intrinsic silicon layer having an electricalconductivity less than 10⁻² siemens per centimeter. Alternately, thesemiconductor material layer can be a p-doped silicon layer or ann-doped silicon layer having a dopant concentration from about 10¹⁴/cm³to about 10²⁰/cm³ (corresponding to an electrical conductivity rangefrom about 10⁻² siemens per centimeter to 10³ siemens per centimeter),and preferably from about 10¹⁴/cm³ to about 10¹⁷/cm³ (corresponding toan electrical conductivity range from about 10⁻² siemens per centimeterto 10 siemens per centimeter). Alternately, the semiconductor materiallayer can include any other semiconductor material such as, but notlimited to, germanium, a silicon-germanium alloy, a silicon-carbonalloy, a silicon-germanium-carbon alloy, gallium arsenide, indiumarsenide, indium phosphide, III-V compound semiconductor materials,II-VI compound semiconductor materials, organic semiconductor materials,or other compound semiconductor materials. Further, in case thesubstrate material layer 10 is a semiconductor material layer, thesemiconductor material layer can be single crystalline, polycrystalline,amorphous, or have a combination of at least two of a single crystallineportion, a polycrystalline portion, and an amorphous portion. In anexample, the substrate 8 can be a silicon substrate, in which case thesubstrate material layer 10 is a single crystalline silicon layer.

In another embodiment, the substrate material layer 10 can include aninsulator material having an electrical conductivity less than 10⁻⁸siemens per centimeter. For example, the insulator material can besilicon oxide, silicon nitride, or any other dielectric material.Further, the substrate material layer 10 can be a combination of atleast one semiconductor layer and at least one insulator layer as in thecase of a semiconductor-on-insulator substrate. The substrate 8 may, ormay not, include an additional layer (not shown) underneath thesubstrate material layer 10. If an additional layer is present, theadditional layer can be a conductive material layer, a semiconductormaterial layer, a dielectric material layer, or a combination thereof.

At least one deep trench 9 is formed in the substrate material layer 10.The at least one deep trench 9 can be formed by employing methods knownin the art. Each of the at least one deep trench 9 has substantiallyvertical sidewalls and can have a substantially horizontal bottomsurface. Typically, the substantially vertical sidewalls of the at leastone deep trench 9 has a taper angle of less than 5 degrees, andpreferably less than 2 degrees, and more preferably less than 1 degree.The taper angle is measured from a vertical line that is perpendicularto the top surface 11 of the substrate 8.

An exemplary method that can be employed to form the at least one deeptrench 9 is described below. A mask layer 6 can be formed on the topsurface 11 of the substrate 8, which is a planar horizontal surfacebefore formation of the at least one deep trench 9. The mask layer 6 canbe composed of a dielectric oxide, a dielectric nitride, a dielectricoxynitride, or a combination thereof. The dielectric oxide can beundoped silicate glass or a doped silicate glass such as borosilicateglass (BSG), borophosphosilicate glass (BPSG), phosphosilicate glass(PSG), a fluorosilicate glass (FSG), or a combination thereof. Examplesof the dielectric nitride and the dielectric oxynitride include siliconnitride and silicon oxynitride. The mask layer 6 can include a stack ofa silicon oxide layer (not shown separately) contacting a top surface ofthe top semiconductor layer 30 and a silicon nitride layer (not shownseparately) located directly on the silicon oxide layer. Typically, themask layer 6 can be formed by chemical vapor deposition (CVD) such aslow pressure chemical vapor deposition (LPCVD), rapid thermal chemicalvapor deposition (RTCVD), plasma enhanced chemical vapor deposition(PECVD), high density plasma chemical vapor deposition (HDPCVD), etc.The thickness of the mask layer 6 can be from 500 nm to 3,000 nm, andtypically from 800 nm to 1,500 nm, although lesser and greaterthicknesses can also be employed.

A photoresist (not shown) is subsequently applied over the mask layer 6.A lithographic pattern including at least one opening is formed in thephotoresist by lithographic exposure and development. A horizontalcross-sectional shape of each of the at least one opening can be acircle, an ellipse, a polygon, or a derivative a polygon derived byrounding corners thereof. A characteristic lateral dimension of theshape of each opening is limited by the printing capability of alithographic tool employed to pattern the opening. The characteristiclateral dimension can be a diameter of a circle, a minor axis of anellipse, a distance between two facing sides of a polygon or aderivative thereof, or a distance that can otherwise characterize aseparation distance between different sides of the shape.

The pattern of each opening in the photoresist is transferred by ananisotropic etch into the mask layer 6 to form at least one opening.During the anisotropic etch that removes exposed portions of the masklayer 6, the photoresist is employed as an etch mask. The width of theat least one opening in the mask layer 6 is typically comparable withthe characteristic lateral dimension of an overlying opening in thephotoresist. The width of the opening in the mask layer 6 can be from 40nm to 200 nm, which is also the characteristic lateral dimension of theoverlying opening in the photoresist. The photoresist is subsequentlyremoved selective to the mask layer 6, for example, by ashing.

The pattern in the mask layer 6 is further transferred into an upperportion of the substrate material layer 10, for example, by anotheranisotropic etch. Exposed portions of the substrate material layer 10are removed from underneath the at least one opening in the mask layer 6during the anisotropic etch to form the at least one deep trench 9therein. The anisotropic etch of the substrate material layer 10 can beperformed either before or after removal of the photoresist. If thepattern in the mask layer 6 is transferred into the substrate materiallayer 10 before removal of the photoresist, the photoresist functions anetch mask. If the pattern in the mask layer 6 is transferred into thetop semiconductor layer after removal of the photoresist, the mask layer6 functions an etch mask. The buried insulator layer 30 can be employedas a stopping layer for the anisotropic etch. The trench 12′ is ashallow trench that vertically extends from a top surface of the topsemiconductor layer 30 to a bottom surface of the top semiconductorlayer 30. The depth of the trench 12′ as measured from the top surfaceof the top semiconductor layer 30 can be the same as the thickness ofthe top semiconductor layer 30.

A first depth d1 of the at least one deep trench 9, as measuredvertically from the top surface 11 of the substrate 8 to a bottomsurface of the at least one deep trench 9, can be from 1 micron to 10microns, and typically from 2 microns to 8 microns. Preferably, theelectrical conductivity of the substrate material layer 10 is notincreased above the level of the electrical conductivity of thesubstrate material layer 10 as originally provided. For example,maintaining the electrical conductivity of the substrate material layer10 can be effected by not implanting any dopant into the substratematerial layer 10 if the substrate material layer 10 includes asemiconductor material. Any remaining portion of the photoresist, ifany, and the mask layer 6 are subsequently removed selected to thematerial of the substrate material layer 10. If the substrate materiallayer 10 is a semiconductor layer, the at least one deep trench 9 islocated in the semiconductor layer in the substrate 8.

Referring to FIG. 2, a stack of material layers is deposited to fill theat least one deep trench 9. The stack of material layers includes, frombottom to top on a horizontal plane or from outside to inside withineach of the at least one deep trench, a first conductive layer 20, afirst node dielectric layer 30, a second conductive layer 40, a secondnode dielectric layer 50, and a third conductive layer 60. The firstconductive layer 20 contiguously contacts a bottom surface and sidewallsof each of the at least one deep trench. The first node dielectric layer30 contiguously contacts sidewalls of the first conductive layer 20.Further, the first node dielectric layer 30 contiguously contacts a topsurface of any horizontal bottom portion of the first conductive layer20 within a deep trench, if the deep trench is sufficiently wide at thebottom to form such a horizontal bottom portion. The second conductivelayer 40 contiguously contacts sidewalls of the first node dielectriclayer 30. Further, the second conductive layer 30 contiguously contactsa top surface of any horizontal bottom portion of the first nodedielectric layer 30 within a deep trench, if the deep trench issufficiently wide at the bottom to form such a horizontal bottomportion. The second node dielectric layer 50 contiguously contactssidewalls of the second conductive layer 40. Further, the second nodedielectric layer 50 contiguously contacts a top surface of anyhorizontal bottom portion of the second conductive layer 40 within adeep trench, if the deep trench is sufficiently wide at the bottom toform such a horizontal bottom portion. The third conductive layer 60contiguously contacts sidewalls of the second node dielectric layer 50.Further, third conductive layer 60 contiguously contacts a top surfaceof any horizontal bottom portion of the second node dielectric layer 50within a deep trench, if the deep trench is sufficiently wide at thebottom to form such a horizontal bottom portion.

The first conductive layer 20, the first node dielectric layer 30, thesecond conductive layer 40, the second node dielectric layer 50, and thethird conductive layer 60 do not include any hole within the at leastone deep trench. Thus, all surfaces of the first node dielectric layer30 that are located within the at least one trench contact the firstconductive layer 20 or the second conductive layer 40. Likewise, allsurfaces of the second node dielectric layer 50 that are located withinthe at least one trench contact the second conductive layer 40 or thethird conductive layer 60.

Each of the first node dielectric layer 30 and the second nodedielectric layer 50 includes a dielectric material, which can bedeposited by employing methods known in the art. For example, thedielectric materials of the first node dielectric layer 30 and thesecond node dielectric layer 50 can be deposited by chemical vapordeposition (CVD), atomic layer deposition (ALD), or a combination ofthereof. Each of the first node dielectric layer 30 and the second nodedielectric layer 50 can include silicon oxide, silicon nitride, a high-kmaterial having a dielectric constant greater than the dielectricconstant of silicon nitride, or any suitable combination of thesematerials. Exemplary high-k materials include a dielectric metal oxideor a dielectric metal oxide-nitride such as HfO₂, ZrO₂, La₂O₃, Al₂O₃,TiO₂, SrTiO₃, LaAlO₃, Y₂O₃, HfO_(x)N_(y), ZrO_(x)N_(y), La₂O_(x)N_(y),Al₂O_(x)N_(y), TiO_(x)N_(y), SrTiO_(x)N_(y), LaAlO_(x)N_(y),Y₂O_(x)N_(y), a silicate thereof, and an alloy thereof. Each value of xis independently from 0.5 to 3 and each value of y is independently from0 to 2. The thickness of the first node dielectric layer 30 can be from2 nm to 20 nm, and preferably from 3 nm to 10 nm, although lesser andgreater thickness can also be employed. Likewise, the thickness of thesecond node dielectric layer 50 can be from 2 nm to 20 nm, andpreferably from 3 nm to 10 nm, although lesser and greater thickness canalso be employed. Preferably, the thicknesses of the first nodedielectric layer 30 and the second node dielectric layer 50 are set at aminimum value that does not increase a leakage current therethroughsignificantly.

Each of the first conductive layer 20, second conductive layer 40, andthe third conductive layer 60 includes a conductive material. In thefirst embodiment, the conductive material of the second conductive layer40 is selected to be different from the conductive material of the firstconductive layer 20 and from the conductive material of the thirdconductive layer 60. Specifically, the conductive material of the secondconductive layer 40 is selected such that an etch chemistry exists thatetches the conductive material of the second conductive layer 40selective to the conductive materials of the first and third conductivelayers (20, 60) and at least another etch chemistry exists that etchesthe conductive materials of the first and/or third conductive layers(20, 60) selective to the conductive material of the second conductivelayer 40. The conductive material of the first conductive layer 20 canbe the same as, or can be different from, the conductive material of thethird conducive material layer 50. Methods of depositing aluminum, analuminum alloy, refractive metals, conductive nitrides of refractivemetals, and doped semiconductor materials are known in the art, andinclude chemical vapor deposition (CVD), atomic layer deposition (ALD),and electroplating, electroless plating.

Etch chemistries are known in the art that etch aluminum selective torefractive metals, conductive nitrides of refractive metals, and dopedsemiconductor materials. Other etch chemistries are known in the artthat etch refractive metals or conductive nitrides of refractive metalsselective to aluminum and doped semiconductor materials. Yet other etchchemistries are known in the art that etch doped semiconductor materialsselective to refractive metals, conductive nitrides of refractivemetals, and aluminum. Preferably, etch chemistries that do not etch thedielectric materials of the first and second node dielectric layers (30,50) are selected.

In one embodiment, the conductive material of the second conductivelayer 40 is composed of aluminum or an aluminum alloy including at least70% of aluminum in atomic composition, and the conductive materials ofthe first and third conductive layers (20, 40) include at least onerefractory metal and/or at least one doped semiconductor material, whichcan be an elemental doped semiconductor material such as Si and Ge, adoped semiconductor alloy including Si and Ge, or a compound dopedsemiconductor material.

In another embodiment, the conductive material of the second conductivelayer 40 is composed of at least one refractive metal and/or at leastone conductive nitride of a refractive metal, and the conductivematerials of the first and third conductive layers (20, 40) includealuminum and/or an aluminum alloy including at least 70% of aluminum inatomic composition and/or at least one doped semiconductor material,which can be a doped elemental semiconductor material such as doped Siand doped Ge, a doped semiconductor alloy including Si and Ge, or adoped compound semiconductor material.

In yet another embodiment, the conductive material of the secondconductive layer 40 is composed of at least one doped semiconductormaterial, which can be a doped elemental semiconductor material such asdoped Si and doped Ge, a doped semiconductor alloy including Si and Ge,or a doped compound semiconductor material, and the conductive materialsof the first and third conductive layers (20, 40) include aluminumand/or an aluminum alloy including at least 70% of aluminum in atomiccomposition and/or at least one refractive metal and/or at least oneconductive nitride of a refractive metal.

The thickness of the first conductive layer 20 can be from 3 nm to 50nm, and typically from 5 nm to 20 nm, although lesser and greaterthicknesses can also be employed The thickness of the second conductivelayer 40 can be from 3 nm to 50 nm, and typically from 5 nm to 20 nm,although lesser and greater thicknesses can also be employed Thethickness of the third conductive layer 60 can be selected to completelyfill the at least one trench, and can be from 3 nm to 150 nm, andtypically from 5 nm to 50 nm, although lesser and greater thicknessescan also be employed. The topmost surface of the third conductive layer60 can be substantially planar if the at least one trench is completelyfilled by the combination of the first conductive layer 20, the firstnode dielectric layer 30, the second conductive layer 40, the secondnode dielectric layer 50, and the third conductive layer 60.

Referring to FIG. 3, the stack of the first conductive layer 20, thefirst node dielectric layer 30, the second conductive layer 40, thesecond node dielectric layer 50, and the third conductive layer 60 canbe lithographically patterned, for example, by a combination ofapplication and lithographic patterning of a photoresist layer (notshown), transfer of the pattern in the photoresist layer into the stackof the first conductive layer 20, the first node dielectric layer 30,the second conductive layer 40, the second node dielectric layer 50, andthe third conductive layer 60, and subsequent removal of the photoresistlayer selective to the third conductive layer 60. An anisotropic etchcan be employed to transfer the pattern in the photoresist layer, whichcan form substantially vertical edge surfaces on each of the firstconductive layer 20, the first node dielectric layer 30, the secondconductive layer 40, the second node dielectric layer 50, and the thirdconductive layer 60. These substantially vertical edge surfaces arevertically coincident with one another, and are located above a topsurface of the substrate.

At least one shallow trench isolation (STI) structure 108 can beoptionally formed in the substrate material layer 10, for example, byforming a shallow trench by an anisotropic etch employing an etch mask(not shown) and by filling the shallow trench with a dielectric materialsuch as silicon oxide, silicon nitride, or a combination thereof. The atleast one STI structure 108 is embedded in the substrate material layer10, which can be a semiconductor layer in some embodiments. If thesubstrate material layer 10 is a semiconductor layer, additionalsemiconductor devices (not shown), such as a field effect transistor ora bipolar transistor, can be formed on the top surface of the substratematerial layer 10 employing methods known in the art.

Each of the at least one STI structure 108 extends from the top surfaceof the substrate material layer 10 to a second depth d2 into thesubstrate material layer 10. The first depth d1 (See FIG. 1) of the atleast one trench is greater than the second depth d2. The second depthd2 is typically from 100 nm to 500 nm, and more typically from 200 nm to400 nm, although lesser and greater thicknesses can also be employed.

A contact-level dielectric layer 70 is deposited over the stack of thefirst conductive layer 20, the first node dielectric layer 30, thesecond conductive layer 40, the second node dielectric layer 50, and thethird conductive layer 60. The contact-level dielectric layer 70includes a dielectric material such as undoped silicate glass (USG),doped silicate glass, porous or non-porous organosilicate glass (OSG),or any other dielectric material that can be employed to embedconductive contact via structures therein as known in the art. The topsurface of the contact-level dielectric layer 70 can be substantiallyplanar. The thickness of the contact-level dielectric layer 70 can befrom 50 nm to 2,000 nm, and typically from 150 nm to 500 nm, althoughlesser and greater thicknesses can also be employed.

Referring to FIG. 4, a first photoresist layer 75 is applied to the topsurface of the contact-level dielectric layer 70 and is lithographicallypatterned to form openings therein. The portions of the contact-leveldielectric layer 70, the third conductive layer 60, the second nodedielectric layer 50, the second conductive layer 40, the first nodedielectric layer 30, and the first conductive layer 20 that underlie theopenings are removed by an anisotropic etch that employs the firstphotoresist layer 75 as an etch mask to form at least one first-type viacavity 71 and at least one second-type via cavity 73. Each of the atleast one first-type via cavity 71 and the at least one second-type viacavity 73 extends through horizontal portions of the first conductivelayer 20, the first node dielectric layer 30, the second conductivelayer 40, the second node dielectric layer 50, and the third conductivelayer 60. Portions of the substrate semiconductor layer 10 can berecessed so that the at least one first-type via cavity 71 and the atleast one second-type via cavity 73 extend underneath the topmostsurface of the substrate material layer 10. In this case, a bottomsurface of the at least one first-type via cavity 71 or the at least onesecond-type via cavity 73 can be recessed below the topmost surface ofthe substrate material layer 10. The lateral dimensions, e.g., adiameter, of the at least one first-type via cavity 71 or the at leastone second-type via cavity 73 can be from 50 nm to 1,000 nm, andtypically from 100 nm to 300 nm, although lesser and greater lateraldimensions can also be employed. The first photoresist layer 75 issubsequently removed.

Referring to FIG. 5, a second photoresist layer 77 is applied to the topsurface of the contact-level dielectric layer 70 and is lithographicallypatterned to cover the at least one first-type via cavity 71, whileexposing the at least one second-type via cavity 73. The at least onefirst-type via cavity 71 is plugged by the second photoresist layer 77so that etchants cannot reach the surfaces of the stack of the thirdconductive layer 60, the second node dielectric layer 50, the secondconductive layer 40, the first node dielectric layer 30, and the firstconductive layer 20 within the at least one first-type via cavity 71 ina subsequent etch step.

Referring to FIG. 6, a first etch is performed to etch the conductivematerial of the second conductive layer 40 selective to the conductivematerials of the first and third conductive layers (20, 60) and thedielectric materials of the first and second node dielectric layers (30,50) within the at least one second-type via cavity 73. The conductivematerial of the second conductive layer 40 is laterally removedselective to conductive materials of the first conductive layer 20 andthe third conductive layer 60 by selecting for the first etch an etchchemistry that prevents any substantial etching of the conductivematerials of the first and third conductive layers (20, 60) and thedielectric materials of the first and second node dielectric layers (30,50). A second peripheral cavity 43 that is contiguous with a second-typevia cavity 73 is formed in each laterally recessed portion of the secondconductive layer 40. The lateral extent of the second peripheral cavity43, i.e., the shortest horizontal distance between the unrecessedvertical surfaces of the first and second node dielectric layers (30,50) and the recessed edge surfaces of the second conductive layer 40,can be from 2 nm to 50 nm, and typically from 5 nm to 20 nm, althoughlesser and greater lateral extents can also be employed. The first etchcan be an isotropic etch such as a wet etch or an isotropic dry etch.The second photoresist layer 77 is subsequently removed.

Referring to FIG. 7, a third photoresist layer 79 is applied to the topsurface of the contact-level dielectric layer 70 and is lithographicallypatterned to cover the at least one second-type via cavity 73, whileexposing the at least one first-type via cavity 71. The at least onesecond-type via cavity 73 is plugged by the third photoresist layer 79so that etchants cannot reach the surfaces of the stack of the thirdconductive layer 60, the second node dielectric layer 50, the secondconductive layer 40, the first node dielectric layer 30, and the firstconductive layer 20 within the at least one second-type via cavity 73 ina subsequent etch step.

Referring to FIG. 8, a second etch is performed to etch the conductivematerial of the first and third conductive layer (20, 60) selective tothe conductive material of the second conductive layer 40 and thedielectric materials of the first and second node dielectric layers (30,50) within the at least one first-type via cavity 71. The conductivematerials of the first and third conductive layers (20, 60) arelaterally removed selective to conductive material of the secondconductive layer 40 by selecting for the second etch an etch chemistrythat prevents any substantial etching of the conductive materials of thesecond conductive layer 40 and the dielectric materials of the first andsecond node dielectric layers (30, 50). A first peripheral cavity 23that is contiguous with a first-type via cavity 71 is formed in eachlaterally recessed portion of the first conductive layer 20. A thirdperipheral cavity 63 that is contiguous with a first-type via cavity 71is formed in each laterally recessed portion of the third conductivelayer 60. The lateral extent of the first peripheral cavity 23, i.e.,the shortest horizontal distance between the unrecessed verticalsurfaces of the first and second node dielectric layers (30, 50) and therecessed edge surfaces of the first conductive layer 20, can be from 2nm to 50 nm, and typically from 5 nm to 20 nm, although lesser andgreater lateral extents can also be employed. The lateral extent of thethird peripheral cavity 63, i.e., the shortest horizontal distancebetween the unrecessed vertical surfaces of the first and second nodedielectric layers (30, 50) and the recessed edge surfaces of the thirdconductive layer 60, can be from 2 nm to 50 nm, and typically from 5 nmto 20 nm, although lesser and greater lateral extents can also beemployed. The second etch can be an isotropic etch such as a wet etch oran isotropic dry etch.

Referring to FIG. 9, the third photoresist layer 79 is subsequentlyremoved.

Referring to FIG. 10, a conductive liner layer 80L may be deposited. Theconductive liner layer 80L includes a conductive material such as TiN,TaN, WN, Ti, Ta, W, or a combination thereof. The conductive liner layer80L can be optional, i.e., may, or may not be present. If present, thethickness of the conductive liner layer 80L can be from 2 nm to 30 nm,and typically from 3 nm to 10 nm, although lesser and greaterthicknesses can also be employed. The conductive liner layer 80L isdeposited in a non-conformal manner. Thus, the conductive liner layer80L is not deposited within the at least one first peripheral cavity 23,the at least one second peripheral cavity 43, and the at least one thirdperipheral cavity 63. One exemplary method for depositing the conductiveliner layer 80L in a non-conformal manner is physical vapor deposition(PVD, i.e., sputtering) and vacuum evaporation.

Referring to FIG. 11, a conductive fill material is deposited on theconductive liner layer 80L if the conductive liner layer 80L is present,or in the at least one first-type via cavity 71 and the at least onesecond-type via cavity if a conductive liner layer 80L is not present.In case the conductive liner layer 80L is present, the conductive fillmaterial can be deposited employing a conformal or a non-conformaldeposition method. In case a conductive liner layer 80L is not present,the conductive fill material is deposited employing a non-conformaldeposition method such as physical vapor deposition. Exemplary methodsof conformal deposition include chemical vapor deposition (PVD),electroless plating, and electroplating.

Excess conductive materials above the top surface of the contact-leveldielectric layer 70 are removed, for example, by chemical mechanicalplanarization (CMP), a recess etch, or a combination thereof. Theremaining portions of the conductive fill material and the conductiveliner layer 80L, if any, that fills the at least one first-type viacavity 71 (See FIG. 10) constitute at least one first contact viastructure 84A. The at least one first contact via structure 84A contactsthe second conductive layer 40. Each of the at least one first contactvia structure 84A is electrically isolated from the first conductivelayer 20 due to a first peripheral cavity 23. Further, each of the atleast one first contact via structure 84A is electrically isolated fromthe third conductive layer 60 due to a third peripheral cavity 63. Eachfirst contact via structure 84A includes a first conductive fill portion82A and may include a first conductive liner portion 80A, which is aremaining portion of the conductive liner layer 80L. Each firstperipheral cavity 23 laterally surrounds a portion of a first conductivevia structure 84A between a bottom surface of the first conductive layer20 and a top surface of the first conductive layer 20. Each thirdperipheral cavity 63 laterally surrounds a portion of a first conductivevia structure 84A between a bottom surface of the third conductive layer60 and a top surface of the third conductive layer 60.

The remaining portions of the conductive fill material and theconductive liner layer 80L, if any, that fills the at least onesecond-type via cavity 73 (See FIG. 10) constitute at least one secondcontact via structure 84B. The at least one second contact via structure84B contacts the first conductive layer 20 and the third conductivelayer 60. Each of the at least one second contact via structure 84B iselectrically isolated from the second conductive layer 40 due to asecond peripheral cavity 43. Each second contact via structure 84Bincludes a second conductive fill portion 82B and may include a secondconductive liner portion 80B, which is a remaining portion of theconductive liner layer 80L. Each second peripheral cavity 43 laterallysurrounds a portion of a second conductive via structure 84B between abottom surface of the second conductive layer 40 and a top surface ofthe second conductive layer 40.

The first conductive layer 20 and the third conductive layer 60 cansubsequently be electrically connected by a metal interconnect structure(not shown) such as at least one metal line and/or at least one metalvia in an interconnect-level dielectric layer (not shown). In this case,the first conductive layer 20 and the third conductive layer 60collectively constitute one node of a capacitor structure, the secondconductive layer 40 constitutes another node of the capacitor structure,and the first and second node dielectric layers (30, 50) collectivelyconstitute a node dielectric of the capacitor structure. This capacitorstructure effectively doubles the area of the capacitor compared with aprior art structure that employs at least one deep trench of acomparable size and number and a single layer of node dielectric.

Referring to FIG. 12, a second exemplary structure according to a secondembodiment of the present disclosure includes a substrate 8, a masklayer 6, and at least one deep trench 9. The substrate 8 includes atleast a semiconductor material layer 110 that includes a semiconductormaterial having an electrical conductivity from 10⁻⁸ siemens percentimeter to 10³ siemens per centimeter, and preferably having anelectrical conductivity from 10⁻⁸ siemens per centimeter to 10 siemensper centimeter. For example, if the semiconductor material layer 110 isa silicon layer, the semiconductor material layer 110 can be anintrinsic silicon layer having an electrical conductivity less than 10⁻²siemens per centimeter. Alternately, the semiconductor material layer110 can be a p-doped silicon layer or an n-doped silicon layer having adopant concentration from about 10¹⁴/cm³ to about 10²⁰/cm³(corresponding to an electrical conductivity range from about 10⁻²siemens per centimeter to 10³ siemens per centimeter), and preferablyfrom about 10¹⁴/cm³ to about 10¹⁷/cm³ (corresponding to an electricalconductivity range from about 10⁻² siemens per centimeter to 10 siemensper centimeter). Alternately, the semiconductor material layer 110 caninclude any other semiconductor material such as, but not limited to,germanium, a silicon-germanium alloy, a silicon-carbon alloy, asilicon-germanium-carbon alloy, gallium arsenide, indium arsenide,indium phosphide, III-V compound semiconductor materials, II-VI compoundsemiconductor materials, organic semiconductor materials, or othercompound semiconductor materials. Further, in case the semiconductormaterial layer 110 is a semiconductor material layer 110, thesemiconductor material layer 110 can be single crystalline,polycrystalline, amorphous, or have a combination of at least two of asingle crystalline portion, a polycrystalline portion, and an amorphousportion. In an example, the substrate 8 can be a silicon substrate, inwhich case the semiconductor material layer 110 is a single crystallinesilicon layer.

At least one deep trench 9 is formed in the semiconductor material layer110. The at least one deep trench 9 can be formed by employing methodsknown in the art. Each of the at least one deep trench 9 hassubstantially vertical sidewalls and can have a substantially horizontalbottom surface. Typically, the substantially vertical sidewalls of theat least one deep trench 9 has a taper angle of less than 5 degrees, andpreferably less than 2 degrees, and more preferably less than 1 degree.The taper angle is measured from a vertical line that is perpendicularto the top surface 11 of the substrate 8. The at least one deep trench 9can be formed, for example, by employing the exemplary method describedabove in the first embodiment.

A first depth d1 of the at least one deep trench 9, as measuredvertically from the top surface 11 of the substrate 8 to a bottomsurface of the at least one deep trench 9, can be from 1 micron to 10microns, and typically from 2 microns to 8 microns. Preferably, theelectrical conductivity of the semiconductor material layer 110 is notincreased above the level of the electrical conductivity of thesemiconductor material layer 110 as originally provided. For example,maintaining the electrical conductivity of the semiconductor materiallayer 110 can be effected by not implanting any dopant into thesemiconductor material layer 110. Any remaining portion of a photoresist(not shown), if any, and the mask layer 6 are subsequently removedselected to the material of the semiconductor material layer 110. If thesemiconductor material layer 110 is a semiconductor layer, the at leastone deep trench 9 is located in the semiconductor layer in the substrate8.

Referring to FIG. 13, a stack of material layers is deposited to fillthe at least one deep trench 9. The stack of material layers includes,from bottom to top on a horizontal plane or from outside to insidewithin each of the at least one deep trench, a first conductive layer20, a first node dielectric layer 30, a second conductive layer 40, asecond node dielectric layer 50, and a third conductive layer 60. Thefirst conductive layer 20 contiguously contacts a bottom surface andsidewalls of each of the at least one deep trench. The first nodedielectric layer 30 contiguously contacts sidewalls of the firstconductive layer 20. Further, the first node dielectric layer 30contiguously contacts a top surface of any horizontal bottom portion ofthe first conductive layer 20 within a deep trench, if the deep trenchis sufficiently wide at the bottom to form such a horizontal bottomportion. The second conductive layer 40 contiguously contacts sidewallsof the first node dielectric layer 30. Further, the second conductivelayer 30 contiguously contacts a top surface of any horizontal bottomportion of the first node dielectric layer 30 within a deep trench, ifthe deep trench is sufficiently wide at the bottom to form such ahorizontal bottom portion. The second node dielectric layer 50contiguously contacts sidewalls of the second conductive layer 40.Further, the second node dielectric layer 50 contiguously contacts a topsurface of any horizontal bottom portion of the second conductive layer40 within a deep trench, if the deep trench is sufficiently wide at thebottom to form such a horizontal bottom portion. The third conductivelayer 60 contiguously contacts sidewalls of the second node dielectriclayer 50. Further, third conductive layer 60 contiguously contacts a topsurface of any horizontal bottom portion of the second node dielectriclayer 50 within a deep trench, if the deep trench is sufficiently wideat the bottom to form such a horizontal bottom portion.

The first conductive layer 20, the first node dielectric layer 30, thesecond conductive layer 40, the second node dielectric layer 50, and thethird conductive layer 60 do not include any hole within the at leastone deep trench. Thus, all surfaces of the first node dielectric layer30 that are located within the at least one trench contact the firstconductive layer 20 or the second conductive layer 40. Likewise, allsurfaces of the second node dielectric layer 50 that are located withinthe at least one trench contact the second conductive layer 40 or thethird conductive layer 60.

Each of the first node dielectric layer 30 and the second nodedielectric layer 50 includes a dielectric material, which can have thesame composition and thickness as in the first embodiment, and can bedeposited employing the same method as in the first embodiment.

Each of the first conductive layer 20, second conductive layer 40, andthe third conductive layer 60 includes a conductive material. Unlike thefirst embodiment, there is no limitation on the selection of theconductive materials of the first, second, and third conductive layers(20, 40, 60) in the second embodiment. In other words, consideration ofthe presence of any etch chemistry that selectively removed oneconductive layer relative to another conductive layer is not necessaryin the second embodiment. Thus, each of the first, second, and thirdconductive layers (20, 40, 60) in the second embodiment can includealuminum, an aluminum alloy, refractive metals, conductive nitrides ofrefractive metals, and doped semiconductor materials, which can be anelemental doped semiconductor material such as Si and Ge, a dopedsemiconductor alloy including Si and Ge, or a compound dopedsemiconductor material. The conductive material of any of the first,second, and third conductive layers (20, 40, 60) can be the same as, orcan be different from, the conductive materials of the other two of thefirst, second, and third conductive layers (20, 40, 60). Methods ofdepositing aluminum, an aluminum alloy, refractive metals, conductivenitrides of refractive metals, and doped semiconductor materials areknown in the art, and include chemical vapor deposition (CVD), atomiclayer deposition (ALD), and electroplating, electroless plating.

The thickness of the first conductive layer 20 can be from 3 nm to 50nm, and typically from 5 nm to 20 nm, although lesser and greaterthicknesses can also be employed The thickness of the second conductivelayer 40 can be from 3 nm to 50 nm, and typically from 5 nm to 20 nm,although lesser and greater thicknesses can also be employed Thethickness of the third conductive layer 60 can be selected to completelyfill the at least one trench, and can be from 3 nm to 150 nm, andtypically from 5 nm to 50 nm, although lesser and greater thicknessescan also be employed. The topmost surface of the third conductive layer60 can be substantially planar if the at least one trench is completelyfilled by the combination of the first conductive layer 20, the firstnode dielectric layer 30, the second conductive layer 40, the secondnode dielectric layer 50, and the third conductive layer 60.

Referring to FIG. 14, a first photoresist layer 157 is applied to thetop surface of the third conductive layer 60. An anisotropic etch isemployed to pattern the stack of the third conductive layer 60, thesecond node dielectric layer 50, the second conductive layer 40, thefirst node dielectric layer 30, and the first conductive layer 20.Substantially vertical edge surfaces are formed on each of the thirdconductive layer 60, the second node dielectric layer 50, the secondconductive layer 40, the first node dielectric layer 30, and the firstconductive layer 20. These substantially vertical edge surfaces arevertically coincident with one another, i.e., coincide with one anotherin a top-down view taken along a direction perpendicular to the topsurface 11 of the substrate 8. All of the substantially vertical edgesurfaces are located above the top surface 11 of the substrate 8.

Referring to FIG. 15, a second photoresist layer 159 is applied to thetop surface of the third conductive layer 60. An etch is employed topattern the third conductive layer 60. Preferably, the etch stops on thesecond node dielectric layer 50. The etch can be selective to thesemiconductor material of the semiconductor material layer 110 and thedielectric material of the second node dielectric layer 50. The etch canbe an isotropic etch such as a wet etch, or can be an anisotropic etchsuch as a reactive ion etch. After the patterning of the thirdconductive layer 60, edge surfaces of the third conductive layer 60overlies the top surface of the second node dielectric layer 50.

Referring to FIG. 16, at least one shallow trench isolation (STI)structure 108 can be optionally formed in the semiconductor materiallayer 110, for example, by forming a shallow trench by an anisotropicetch employing an etch mask (not shown) and by filling the shallowtrench with a dielectric material such as silicon oxide, siliconnitride, or a combination thereof. The at least one STI structure 108 isembedded in the semiconductor material layer 110, which can be asemiconductor layer in some embodiments. Additional semiconductordevices (not shown), such as a field effect transistor or a bipolartransistor, can be formed on the top surface of the semiconductormaterial layer 110 employing methods known in the art.

Each of the at least one STI structure 108 extends from the top surfaceof the substrate material layer 10 to a second depth d2 into thesemiconductor material layer 110. The first depth d1 (See FIG. 12) ofthe at least one trench is greater than the second depth d2. The seconddepth d2 is typically from 100 nm to 500 nm, and more typically from 200nm to 400 nm, although lesser and greater thicknesses can also beemployed.

At least one metal-semiconductor-alloy region 118 is formed at portionsof the top surface of the semiconductor material layer 110. The at leastone metal-semiconductor-alloy region 118 can be formed by depositing ametal layer on at least one area of the top surface of the semiconductormaterial layer 110, and inducing a reaction between the metal layer andthe semiconductor material underneath. In case the semiconductormaterial layer 110 includes silicon, the metal-semiconductor-alloyregion 118 can include a metal silicide. In case the semiconductormaterial layer 110 includes germanium, the metal-semiconductor-alloyregion 118 can include a metal germanide. The at least onemetal-semiconductor-alloy region 118 is located in the substrate 8 andcontacting a peripheral bottom surface of the first conductive layer 20.

The area on which the at least one metal-semiconductor-alloy region 118is formed can be defined by employing a patterned dielectric mask layer(not shown), which can be removed after forming the at least onemetal-semiconductor-alloy region 118. The at least onemetal-semiconductor-alloy region 118 contacts a peripheral bottomsurface of the first conductive layer 20, and can be laterally limitedby the at least one STI structure 108. Electrical dopants (e.g., p-typedopants or n-type dopants) can be implanted near the area of contactbetween the second conductive layer 20 and the at least onemetal-semiconductor-alloy region 118 to reduce the electrical resistancebetween the at least one metal-semiconductor-alloy region 118 and thefirst conductive layer 20.

Referring to FIG. 17, a contact-level dielectric layer 70 is depositedover the stack of the first conductive layer 20, the first nodedielectric layer 30, the second conductive layer 40, the second nodedielectric layer 50, and the third conductive layer 60. Thecontact-level dielectric layer 70 can have the same composition andthickness as in the first embodiment, and can be formed employing thesame method as in the first embodiment.

Various via cavities are formed in the contact-level dielectric layer70, for example, by applying and lithographically patterning aphotoresist layer to form openings therein and by transferring thepattern of openings in the photoresist layer into the contact-leveldielectric layer 70 by an anisotropic etch. The anisotropic etch canemploy a chemistry that stops on a metallic material such as theconductive material of the third conductive layer 60, the conductivematerial of the second conductive layer 40, and themetal-semiconductor-alloy in the at least one metal-semiconductor-alloyregion 118, while etching through the dielectric material of thecontact-level dielectric layer 70 and the second node dielectric layer50. At least one first contact via structure 182 contacting the at leastone metal-semiconductor-alloy region 118, at least one second contactvia structure 184 contacting the second conductive layer 40, and atleast one third contact via structure 186 contacting the thirdconductive layer 60 are formed by filling the various via cavities.

The first conductive layer 20 and the third conductive layer 60 cansubsequently be electrically connected by a metal interconnect structure(not shown) such as at least one metal line and/or at least one metalvia in an interconnect-level dielectric layer (not shown). In this case,the first conductive layer 20 and the third conductive layer 60collectively constitute one node of a capacitor structure, the secondconductive layer 40 constitutes another node of the capacitor structure,and the first and second node dielectric layers (30, 50) collectivelyconstitute a node dielectric of the capacitor structure. This capacitorstructure effectively doubles the area of the capacitor compared with aprior art structure that employs at least one deep trench of acomparable size and number and a single layer of a node dielectric.

Referring to FIG. 18, a third exemplary structure according to a thirdembodiment of the present disclosure is the same as the first exemplarystructure of FIG. 3, and can be formed employing the same processingsteps as in the first embodiment.

Referring to FIG. 19, a first photoresist layer 275 is applied to thetop surface of the contact-level dielectric layer 70 and islithographically patterned to form openings therein. The portions of thecontact-level dielectric layer 70 underlie the openings are removed byan anisotropic etch that employs the first photoresist layer 75 as anetch mask to form at least one first-type via cavity 271, at least onesecond-type via cavity 272, and at least one third-type via cavity 273within the contact-level dielectric layer 70. A top surface of the thirdconductive layer 60 is exposed at the bottom of each of the at least onefirst-type via cavity 271, the at least one second-type via cavity 272,and the at least one third-type via cavity 273. The first photoresistlayer 275 is subsequently removed.

Referring to FIG. 20, a second photoresist layer 277 is applied to thetop surface of the contact-level dielectric layer 70 and islithographically patterned to cover the at least one third-type viacavity 273 (See FIG. 19), while exposing the at least one second-typevia cavity 272 and the at least one first-type via cavity 271. The upperportion of the third exemplary structure is exposed to at least one etchthat removes exposed portions of the third conductive layer 60 and thesecond node dielectric layer 50 that underlie the at least onesecond-type via cavity 272 and the at least one first-type via cavity271. The second photoresist layer 277 and the contact-level dielectriclayer 70 collectively function as an etch mask during the at least oneetch, which can include an isotropic etch and/or an anisotropic etch.Exemplary isotropic etch processes include wet etch processes andisotropic dry etch processes, and exemplary anisotropic etch processinclude reactive ion etch processes. The at least one second-type viacavity 272 and the at least one first-type via cavity 271 are verticallyexpanded so that a top surface of the second conductive layer 40 isexposed at the bottom of each of the at least one second-type via cavity272 and the at least one first-type via cavity 271. The secondphotoresist layer 277 is subsequently removed.

Referring to FIG. 21, a third photoresist layer 279 is applied to thetop surface of the contact-level dielectric layer 70 and islithographically patterned to cover the at least one third-type viacavity 273 and the at least one second type via cavity 272 (See FIG.19), while exposing the at least one first-type via cavity 271. Theupper portion of the third exemplary structure is exposed to at leastone etch that removes exposed portions of the second conductive layer 40and the first node dielectric layer 30 that underlie the at least onefirst-type via cavity 271. The third photoresist layer 279 and thecontact-level dielectric layer 70 collectively function as an etch maskduring the at least one etch, which can include an isotropic etch and/oran anisotropic etch. Exemplary isotropic etch processes include wet etchprocesses and isotropic dry etch processes, and exemplary anisotropicetch process include reactive ion etch processes. The at least onefirst-type via cavity 271 is vertically expanded so that a top surfaceof the first conductive layer 20 is exposed at the bottom of each of theat least one first-type via cavity 271.

Referring to FIG. 22, the third photoresist layer 279 is subsequentlyremoved.

Referring to FIG. 23, a dielectric liner 290L is deposited on the topsurface and sidewall surfaces of the contact-level dielectric layer 70,sidewall surfaces of the third conductive layer 60, the second nodedielectric layer 50, the second conductive layer 40, and the first nodedielectric layer 30, and exposed top surfaces of the first conductivelayer 20. The dielectric liner 290L includes a dielectric material suchas silicon oxide, silicon nitride, and/or organosilicate glass (OSG).The dielectric liner 290L can be a conformal layer, and can bedeposited, for example, by chemical vapor deposition (CVD). Thethickness of the dielectric liner 290L, as measured at the bottom ofsidewall portions within the via cavities, can be from 3 nm to 50 nm,and typically from 5 nm to 20 nm, although lesser and greaterthicknesses can also be employed.

Referring to FIG. 24, an anisotropic etch is performed to removehorizontal portions of the dielectric liner 290L. Each remainingvertical portion of the dielectric liner 290L constitutes a dielectricspacer 290, which covers sidewall surfaces of the contact-leveldielectric layer 70, the third conductive layer 60, the second nodedielectric layer 50, the second conductive layer 40, and the first nodedielectric layer 30. A top surface of the first conductive layer 20, atop surface of the second conductive layer 40, or a top surface of thethird conductive layer 60 is exposed at a bottom of in each via cavity.

A conductive fill material is deposited to fill the via cavities thatare lined with the dielectric spacers 290. Exemplary methods ofdepositing the conductive fill material include chemical vapordeposition (PVD), electroless plating, and electroplating. Excessconductive materials above the top surface of the contact-leveldielectric layer 70 are removed, for example, by chemical mechanicalplanarization (CMP), a recess etch, or a combination thereof. Theremaining portions of the conductive fill material constitute variouscontact via structures, which include a first-type contact via structure291 that contacts a top surface of the first conductive layer 20, asecond-type contact via structure 292 that contacts a top surface of thesecond conductive layer 40, and a third-type contact via structure 293that contacts a top surface of the third conductive layer 60. Eachfirst-type contact via structure 291 is electrically isolated from thesecond and third conductive layers (40, 60) by a dielectric spacer 290,and each second-type contact via structure 292 is electrically isolatedfrom the third conductive layer 60 by a dielectric spacer 290.

The first conductive layer 20 and the third conductive layer 60 cansubsequently be electrically connected by a metal interconnect structure(not shown) such as at least one metal line and/or at least one metalvia in an interconnect-level dielectric layer (not shown). In this case,the first conductive layer 20 and the third conductive layer 60collectively constitute one node of a capacitor structure, the secondconductive layer 40 constitutes another node of the capacitor structure,and the first and second node dielectric layers (30, 50) collectivelyconstitute a node dielectric of the capacitor structure. This capacitorstructure effectively doubles the area of the capacitor compared with aprior art structure that employs at least one deep trench of acomparable size and number and a single layer of node dielectric.

While the disclosure has been described in terms of specificembodiments, it is evident in view of the foregoing description thatnumerous alternatives, modifications and variations will be apparent tothose skilled in the art. Accordingly, the disclosure is intended toencompass all such alternatives, modifications and variations which fallwithin the scope and spirit of the disclosure and the following claims.

What is claimed is:
 1. A structure including a capacitor structure, saidcapacitor structure comprising: a trench located in a substrate; a firstconductive layer contiguously contacting a bottom surface and sidewallsof said trench; a first node dielectric layer contiguously contactingsidewalls of said first conductive layer; a second conductive layercontiguously contacting sidewalls of said first node dielectric layer; asecond node dielectric layer contiguously contacting sidewalls of saidsecond conductive layer; and a third conductive layer contiguouslycontacting sidewalls of said second node dielectric layer.
 2. Thestructure of claim 1, wherein all surfaces of said first node dielectriclayer that are located within said trench contact said first conductivelayer or said second conductive layer.
 3. The structure of claim 2,wherein all surfaces of said second node dielectric layer that arelocated within said trench contact said second conductive layer or saidthird conductive layer.
 4. The structure of claim 1, wherein said trenchis located in a semiconductor layer in said substrate.
 5. The structureof claim 4, further comprising a shallow trench isolation (STI)structure embedded in said semiconductor layer, wherein said STIstructure comprises a dielectric material.
 6. The structure of claim 5,wherein said STI structure extends from a top surface of saidsemiconductor layer to a depth into said semiconductor layer, and saidtrench extends from said top surface to another depth that is greaterthan said depth.
 7. The structure of claim 1, wherein substantiallyvertical edge surfaces of each of said first conductive layer, saidfirst node dielectric layer, said second conductive layer, said secondnode dielectric layer, and said third conductive layer are verticallycoincident with one another, and are located above a top surface of saidsubstrate.
 8. The structure of claim 7, further comprising a contact viastructure that contacts said first conductive layer and said thirdconductive layer.
 9. The structure of claim 8, further comprising aperipheral cavity laterally surrounding a portion of said conductive viastructure between a bottom surface of said second conductive layer and atop surface of said second conductive layer.
 10. The structure of claim8, further comprising another contact via structure that contacts saidsecond conductive layer and electrically isolated from said firstconductive layer and said third conductive layer.
 11. The structure ofclaim 10, further comprising: a peripheral cavity laterally surroundinga portion of said another conductive via structure between a bottomsurface of said first conductive layer and a top surface of said firstconductive layer; and another peripheral cavity laterally surroundinganother portion of said another conductive via structure between abottom surface of said third conductive layer and a top surface of saidthird conductive layer.
 12. The structure of claim 7, furthercomprising: a first contact via structure that contacts a top surface ofsaid third conductive layer and laterally surrounded by a firstdielectric spacer; a second contact via structure that contacts a topsurface of said second conductive layer and laterally spaced from saidthird conductive layer by a second dielectric spacer; and a thirdcontact via structure that contacts a top surface of said firstconductive layer and laterally spaced from said second conductive layerand said third conductive layer by a third dielectric spacer.
 13. Thestructure of claim 12, wherein said first contact via structure and saidthird contact via structure are electrically connected to each other andare electrically isolated from said second contact via structure. 14.The structure of claim 1, wherein substantially vertical edge surfacesof each of said first conductive layer, said first node dielectriclayer, said second conductive layer, and said second node dielectriclayer are vertically coincident with one another, and are located abovea top surface of said substrate, and edge surfaces of said thirdconductive layer overlies a top surface of said second node dielectriclayer.
 15. The structure of claim 14, further comprising ametal-semiconductor-alloy region located in said substrate andcontacting a peripheral bottom surface of said first conductive layer.16. A method of forming a structure including a capacitor structure,said method comprising: forming a trench in a substrate; forming a firstconductive layer contiguously contacting a bottom surface and sidewallsof said trench; forming a first node dielectric layer contiguouslycontacting sidewalls of said first conductive layer; forming a secondconductive layer contiguously contacting sidewalls of said first nodedielectric layer; forming a second node dielectric layer contiguouslycontacting sidewalls of said second conductive layer; and forming athird conductive layer contiguously contacting sidewalls of said secondnode dielectric layer, wherein said first conductive layer, said firstnode dielectric layer, said second conductive layer, said second nodedielectric layer, and said third conductive layer collectively form acapacitor structure.
 17. The method of claim 16, further comprisingforming a contact via structure that contacts said first conductivelayer and said third conductive layer, wherein said contact viastructure is electrically isolated from said second conductive layer.18. The method of claim 17, further comprising: forming a via cavitythat extends through said first conductive layer, said first nodedielectric layer, said second conductive layer, said second nodedielectric layer, and said third conductive layer; and laterallyremoving a material of said second conductive layer selective tomaterials of said first conductive layer and said third conductivelayer, wherein said contact via structure is formed by filling said viacavity with a conductive material.
 19. The method of claim 16, furthercomprising: forming a first contact via structure that contacts a topsurface of said third conductive layer and laterally surrounded by afirst dielectric spacer; forming a second contact via structure thatcontacts a top surface of said second conductive layer and laterallyspaced from said third conductive layer by a second dielectric spacer;and forming a third contact via structure that contacts a top surface ofsaid first conductive layer and laterally spaced from said secondconductive layer and said third conductive layer by a third dielectricspacer.
 20. The method of claim 16, further comprising forming ametal-semiconductor-alloy region in said substrate, wherein saidmetal-semiconductor alloy region contacts a peripheral bottom surface ofsaid first conductive layer.